Compost is the one garden container a cat can climb into, stay warm in, and leave with mold on its paws. The hazard is not bacterial: penitrem A, a tremorgenic mycotoxin from Penicillium crustosum and its relatives, can start whole-body tremors 15 minutes after a meal of moldy scraps. The ASPCA Animal Poison Control Center had consulted on 25 suspected canine cases and 1 squirrel by the time its toxicology brief was published, and there is still no published feline case. That missing number shapes everything below: this is a page about access and observation, not about a disease cats are known to get.
What is actually growing in the bin
Compost is a warm, wet, sugar-and-protein buffet, the same conditions that grow mold indoors, and exactly what Penicillium wants. The species most often implicated is P. crustosum, and it does not need to show as green fur to be dangerous. The toxins are penitrems A and E, roquefortine C, verruculogen and the thomitrems; at least 20 mycotoxins are classed as tremorgens, though only a few matter clinically.
The substrates read like a fridge cleanout: moldy dairy, walnuts, peanuts, pasta, stored grain, silage, food waste. Merck makes a point owners find counterintuitive: absence of visible fungus does not exclude mycotoxicosis, because the toxin outlives the mold. Scraping the green off a yogurt tub does not make the rest safe.
Why cats have almost no case reports
Published penitrem A toxicosis exists for dogs, cattle, sheep, rabbits, poultry, rodents, guinea pigs and calves. For cats the literature is silent, and the usual explanation is not resistance but appetite: a cat is far less likely than a Labrador to finish a rotting windfall apple.
Silence is not safety. The mechanism is central-nervous and species-generic, and ASPCA clinicians note that tremor calls about cats do arrive. A cat's routes are narrower but real: licking leachate off the lid, grooming mold off its paws after digging for mice, chewing a moldy rind, or sharing a garden with a dog that drags scraps to the door.
The clock: 15 minutes to 12 hours
Penitrem A is absorbed fast. Onset has been documented at 15 minutes, with larger doses producing faster signs; at low doses the first tremor can be delayed 12 hours or more. Merck gives 1 to 2 hours as the common window. Vomiting often comes first, which is protective, and it appeared in 13 of 26 APCC consultations.
| Clock | What you see | What it means |
|---|---|---|
| 0 to 15 minutes | Vomiting, salivation, lip licking | Often the only chance for decontamination |
| 15 minutes to 3 hours | Fine shoulder tremors, twitching ears, unsteady walk | The classic window; handling makes it worse |
| 1 to 6 hours | Above 39.5 C, fast heart rate, dilated pupils | Muscle work is heating the cat inside |
| 6 to 24 hours | Tremors peak; large doses reach seizures | Sedation and cooling, not more waiting |
| 24 to 48 hours | Most patients settle | Full recovery is the usual outcome |
| Weeks to years | Rare residual ataxia | Seen in dogs at 7 months and 3 years |
A tremor is not a seizure
The distinction decides the phone call. A tremorgenic patient is present: it tracks you, reacts to sound, and shakes harder when touched, because sound and handling amplify intention tremor. Expect ataxia, hyperesthesia, nystagmus, tachycardia and heavy salivation. A seizing patient is not present; it paddles and loses consciousness.
Toxic differentials include pyrethroid spot-ons, a common feline mistake, plus metaldehyde, strychnine, bromethalin, organophosphates, caffeine, ivermectin and ethylene glycol. Non-toxic ones include low glucose and low calcium, liver encephalopathy, cerebellar disease, distemper and rabies.
Heat is the part that kills
Tremors are muscular work, and continuous work pushes core temperature past 40 C within hours. That is where the serious damage starts: hyperthermia can trigger disseminated intravascular coagulation, and muscle breakdown releases myoglobin that loads the kidneys. Cooling has a hard stop at 102.5 F, or 39.2 C; go below that and the cat rebounds into hypothermia. No ice baths or alcohol rubs on the way to the clinic.
What the clinic does in the first hour
Rapid absorption compresses the decontamination window. Emesis or activated charcoal helps only if the cat is seen early and is stable; gastric lavage may be used when imaging shows a stomach full of compost, weighing aspiration risk. Tremor control comes next, with a sedative or muscle relaxant chosen and dosed by the veterinarian, plus fluids, antiemetics and active cooling.
For refractory cases, intravenous lipid emulsion is reported as a rescue: in 53 dogs with suspected tremorgenic mycotoxicosis, 96 percent improved after infusion, median time to improvement 4 hours, with no adverse effects recorded. Most patients are normal within days; a minority of dogs stay ataxic for months.
Three retrofits that end the access
A working heap runs at 32 to 60 C, most of its microbes die above 60 C, and above 71 C it can sterilize itself. Heat kills the fungus, not the toxin already produced, so a hot pile is not a safe route for moldy food.
- Seal the lid. A latch plus a 10 kg weight or a strap stops a cat lifting it; check the hinge twice a year.
- Close the base. A 13 mm hardware cloth floor and a 30 cm outward skirt stop digging under the frame, which is how most cats enter.
- Change what goes in. No dairy, meat, pasta, nuts or cooked food, because those are the substrates. Use a sealed caddy or bokashi bin for scraps and keep the heap for garden waste.
The six-hour watch at home
If you know the cat has been in the bin, note the time and what it ate, then close the bin. Do not induce vomiting at home: aspiration pneumonia is a documented complication and a trembling cat aspirates easily. Call the ASPCA Animal Poison Control Center on 888-426-4435 or your vet, and take the moldy material with you.
At 6 hours, a cat with no vomiting, no tremor at rest, a normal temperature and normal interest in water is low risk. Because low-dose onset can exceed 12 hours, keep it indoors and recheck at 12. Go at once for tremors at rest, a temperature above 39.5 C, reluctance to walk, seizures, or pupils that stop reacting to light.
This article is not a substitute for veterinary diagnosis. Tremors have at least a dozen causes that no web page can separate, and a trembling cat needs a physical examination, a temperature and a blood glucose reading. If you suspect mold exposure, call a poison control service or an emergency clinic rather than waiting to see what happens.
Terms mentioned in this article
Frequently asked
Can a cat get penitrem A poisoning from compost?
It is biologically possible, and there are no published feline cases, which is not the same as no risk. Cats are exposed by licking leachate, grooming mold off their paws after digging, or chewing a moldy rind. Penitrem A acts on the central nervous system in every species tested, so a cat with tremors and compost access should be treated as a suspect case: temperature, glucose and a physical exam first.
How fast do tremors start after eating moldy food?
As fast as 15 minutes with a large dose. Merck gives 1 to 2 hours as the usual window, up to several hours, and low-dose exposures can delay the first tremor by 12 hours or more. That spread is why a cat with a known exposure is kept indoors and watched to 12 hours, not 2.
Does cooking or composting destroy the toxin?
No. Mycotoxins are generally heat-stable, and Merck notes that poisoning can occur when no fungus is detectable, because the toxin outlives the mold. A heap at 55 to 60 C kills much of the fungal growth but does not neutralise toxin already formed, so moldy scraps belong in sealed waste, not the pile.